Flexible hoses or tubes are disposed within various different types of apparatus and structures. While the more commonly used bellows are generally satisfactory with respect to duration and flexibility characteristics, the manufacture of the same is relatively expensive. Ventilation hoses normally employed within vehicles are generally made from soft PVC, however, due to their relative hardness they exhibit a substantial resistance to lateral bending, and exhibit only limited flexibility. A further disadvantage of these hoses resides in the fact that they produce chatter noises when they encounter vehicle parts.
German patent 39 29 051 (see equivalent U.S. Pat. No. 5,060,697) discloses a drainage or ventilation hose comprising a tubular hose body made of soft PVC and having axially spaced, radially extending ribs of chlorinated polyethylene, with the wall thickness of the ribs being relatively small as compared with that of the hose body. The ribs are coextruded along with the hose body. The ribs being relatively soft and having a Shore hardness of 55-65, noise silencing is good as compared to that of smooth PVC hoses and also with respect to ribbed PVC hoses, the ribs also being made from soft PVC.
Due to the inherent characteristics of the soft PVC, the wall of the hose body of this prior art hose only exhibits limited flexibility which cannot be increased by reducing the wall thickness because this would result in a poor resistance to lateral bending. The purpose of the ribs is to silence noises resulting from the hose encountering vehicles parts.